Assessment of Connectivity of Mass Transport Deposits in the Subsurface Using Seismic-Scale Outcrop Analogues

Garyfalou, Katerina¹, Benjamin Kneller¹, Mason Dykstra², David Macdonald¹ (1) University of Aberdeen, Aberdeen, United Kingdom (2) University of California, Santa Barbara, CA

We present a new approach to the assessment of the effectiveness of mass transport deposits (MTDs) as baffles or barriers to fluid flow in the subsurface. We use data from outcrop analogues at a range of length scales (100 to 102 meters]), and representing different textural types of MTDs; >100 m thick mud-rich debris-flow dominated deposit from the Guandacól Formation (Carboniferous, La Rioja Province, NW Argentina; >200m thick slide complex from the Fossil Bluff Group (Jurassic, Alexander Island, Antarctica); 5 m thick sand-rich debris flow deposits from the Grès de Peira Cava (Oligocene, SE France).

Using meso-(core)scale outcrop descriptions of parameters that affect connectivity (net:gross, domain size, fragmentation) we are able to calculate the connectivity in 3D by transforming outcrop data from 2D to 3D. Correlation of each of these parameters with connectivity allows us to identify a range of values over which occurs the transition from effectively disconnected to effectively connected volumes. This transition can be described by percolation theory. If this range of values is treated as a rough threshold, and taking a threshold for each of the three critical parameters, allows us to define a diffuse surface in three (or more) parameter space that separates connected volumes from non-connected volumes. This allows us to differentiate between MTDs that are complete or leaky barriers, baffles, or even potential reservoirs, in the subsurface.